1. Field of the Invention
This invention relates to a liquid storage vessel or tank and particularly to a welded vessel used for the storage of chemicals, heating oil, water, and liquids compatible with high density polyethylene.
2. Description of the Related Art
Steel basement tanks have been in existence for many years. These types of tanks have primarily been used for storage of heating oils. A major drawback for a steel storage tank is that condensation that naturally occurs in the tank causes water to gather at the bottom of the tank. The presence of the water in conjunction with microbial growth that is often present in fuel oil, can cause bacteria to grow which can deteriorate the steel shell of the tank.
Steel tanks can only be used store certain chemicals. Some chemicals react with steel and therefore can not be stored in standard steel tanks.
Additionally in steel tanks used to store chemicals that do not react with steel, condensation causes water to gather on the top and bottom surface of the tank and this can cause imperfections to grow and small portions of the steel to react and thereby adding impurities into the liquid itself and/or cause corrosion of the tank itself.
Many methods have been used with varying success to eliminate moisture in tanks such as desiccant filters and sloping the tank to a drain to remove moisture at the bottom of the tank. These methods work in some cases but not all. The best attempt to solve the problem is to place a person entry known as a manway into a tank, grit blasting the inside of the tank, and applying a liquid based coating to the inside of the tank. This has been done in the industry for years. However for smaller tanks this is cost prohibitive therefore creating a need to find a method for protecting the inside of the tank without having to have a person physically enter the tank.
There is no known effective method or apparatus for protecting the inside of the tank from condensation and water build up without having a person enter the inside of the tank.
The present invention solves this problem by coating a lap welded tank with a perforation in the lap weld with granular polyethylene and then heating the tank. The polyethylene also makes it possible to store chemicals that react with steel.
The present invention provides a liquid storage tank for holding chemicals and heating oil and water and liquids compatible with high-density polyethylene. The tank is lap welded with a perforation in the lap weld. The tank also has a polyethylene lining inside of the tank that assumes the shape of the interior of tank. The polyethylene lining may have sufficient strength to hold its shape independent of the tank.
The invention also provides for a liquid storage tank where the perforation is welded closed.
The present invention provides a method for making a liquid storage tank for holding chemicals and heating oils and water and liquids compatible with high-density polyethylene by providing a tank having an opening to receive fluid with lap welded joints and a perforation in the lap joint on each of a cross seam joint and a circumferential joint of the tank. Polyethylene in granular form is inserted into the tank. The tank is heated which causes the polyethylene to melt. The tank can be heated between 300-600xc2x0 F. The tank can also be rotated while it is being heated. The perforations are then welded closed.